ABS function
ABS calculates the absolute value of a number, where that number can be a literal or an expression that evaluates to a number.
Syntax
ABS (number)
Arguments
 number

Number or expression that evaluates to a number. It can be the SMALLINT, INTEGER, BIGINT, DECIMAL, FLOAT4, FLOAT8, or SUPER type.
Return type
ABS returns the same data type as its argument.
Examples
Calculate the absolute value of 38:
select abs (38); abs  38 (1 row)
Calculate the absolute value of (1476):
select abs (1476); abs  62 (1 row)